Yes I know, but that digikey is $5.79 or there abouts.
and sure it's a very good solution (and I appreciate you putting that on the board, very good thinking...)

however, where's the harm in hacking a solution that allows the shift lock to behave more or less as GOD had
intended.

I do have a question,... Because the shift lock is the only thing on that line, would it be feasable to do this with just the 555 toggle circuit and use the shift lock momentary switch to set and reset the output of the 555 and feed the hi or low directly into pin 2 of U4? this line to pin 2

here is what I as thinking: replacing D4 with a tiny 5volt relay....it will produce a nice click as if it
was coming from the switch itself....

You can use that circuit. A flip-flop would work as well, but wouldn't be much smaller, and you'd still want an RC network to debounce. You don't need a relay. You can use the pin to drive an N-FET or NPN transistor at the switch position in the keyboard matrix.

If you really want a relay for the click, then you don't even need the IC. Just use a 2 x form C latching relay (2 SPTD switches in a small DIP package), one resistor, and one capacitor. One relay circuit to close the switch position in the keyboard matrix (where you have the relay now), and the other side to switch back and forth between the opening and closing coils. You'd power the coils from a capacitor, through the cherry MX momentary switch. When the switch is open, the capacitor charges through a resistor. When the switch is closed, it dumps just enough energy to energize the coil, and then would be held low by the opposite coil after the switch until the key is released.

I do have a question,... Because the shift lock is the only thing on that line, would it be feasable to do this with just the 555 toggle circuit and use the shift lock momentary switch to set and reset the output of the 555 and feed the hi or low directly into pin 2 of U4? this line to pin 2

Not really, because even though it's the only switch on that column, the column is only pulled low by the switch when that row is scanned (brought low by U2). Otherwise, that column is pulled high even if the switch is closed.

But, you can use the output to control a transistor (bipolar or FET) across the switch position in the matrix.

If you really want a relay for the click, then you don't even need the IC. Just use a 2 x form C latching relay (2 SPTD switches in a small DIP package), one resistor, and one capacitor. One relay circuit to close the switch position in the keyboard matrix (where you have the relay now), and the other side to switch back and forth between the opening and closing coils. You'd power the coils from a capacitor, through the cherry MX momentary switch. When the switch is open, the capacitor charges through a resistor. When the switch is closed, it dumps just enough energy to energize the coil, and then would be held low by the opposite coil after the switch until the key is released.

So just a few notes before I post some pictures of my board so far.
She is working fine. I did some little changes to it.

Upgraded the serial port to 9600 by jumpering Pin2 of U57 to pin 2 of U30 available
to the right of U60 as shown below. I also added two serial port activity LED's

First I removed both Q1 and Q2. (I'm using TTL Level out to J3).
I removed R64, R62,R63, R72, and D16.
I removed R65 and put a Jumper in place.
Jumper from U62 pin 12 (at the right side of R33) to the collector of Q1.

Pin 3 of J3 is no longer CTS, I'm using it for RX.

Pin 1 is Gnd.
Pin 2 is TX
Pin 3 is RX

The other mod I did was to add RX and TX Leds to the motherboard.
To do this, I put a 74LS14 in the U68 sucket in place of the 7417 chip.
I connected the output of Pin 8 to a Green led to ground in the unused portion of the 20ma loop area, for TX activitiy.
I cut the trace top layer, under the socket for U14 right at Pin 5. I want to use that track to get an activity LED for RX. I jumpered that trace to pin 2 so the RX signal would be fed into 74LS14 pin 13. I then connected a RED LED from the output of 74LS14 pin 12 for RX activity.

Yesterday Steve Gray and I completed the construction of his OSI 600 REV D.
After a bit of trouble shooting, we tracked down to two dodgy chips (sometimes it pays not not buy surplus chips...) and one 16pin socket issue. Now we have two units running side by side.

It's not often you find folks in the same corner of the world with the interest in the same "obscure" vintage computer, but having three folks within 30 minutes of each other is pretty cool

Of the three 600 REV D boards we purchased together with key caps etc, (Josh Bensadon, has the third, and should be beginning construction soon) we have two built and running.

Steve's board is also modified to do 9600 (and 19200 when in 48 character mode...lol like mine), he opted out on the Blinky lights for RX and TX, ok it was getting late, but I think he should do it.)